port-i386/53383: i386 tests panic under qemu with x86/identcpu.c 1.72

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         53383
>Category:       port-i386
>Synopsis:       i386 tests panic under qemu with x86/identcpu.c 1.72
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 18 10:40:00 +0000 2018
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2018.06.17.07.13.02
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

Since the commit

 2018.06.17.07.13.02 maxv src/sys/arch/x86/x86/identcpu.c 1.72

the i386 test runs on the TNF testbed are panicing, as seen in the
following console output:

net/net/t_forwarding (428/759): 6 test cases
    ipforwarding_fastforward_v4: [38.869879s] Passed.
    ipforwarding_fastforward_v6: [42.693007s] Passed.
    ipforwarding_fragment_v4: [43.053724s] Passed.
    ipforwarding_misc: [79.858593s] Passed.
    ipforwarding_v4: [55.624037s] Passed.
    ipforwarding_v6: [72.979567s] Passed.
[333.552765s]

[ 6727.3164359] panic: kernel diagnostic assertion "pcb->pcb_fpcpu == NULL" failed: file "/tmp/bracket/build/2018.06.17.13.12.25-i386/src/sys/arch/x86/x86/fpu.c", line 345
[ 6727.3164359] cpu0: Begin traceback...
[ 6727.3164359] vpanic(c0fc6f80,c939ad9c,c939adbc,c011e886,c0fc6f80,c0fc6ebf,c0fc8289,c0fc834c,159,c8f64000) at netbsd:vpanic+0x132
[ 6727.3164359] kern_assert(c0fc6f80,c0fc6ebf,c0fc8289,c0fc834c,159,c8f64000,c24b6020,c24b6020,c2504aa0,c939ae2c) at netbsd:kern_assert+0x23
[ 6727.3164359] fpu_eagerswitch(c24b6020,c2504aa0,0,c124dc80,0,c24b6020,c092f720,c24b6020,c2504aa0,0) at netbsd:fpu_eagerswitch+0xe0
[ 6727.3164359] cpu_switchto(c24b6020,c17c7d40,c939ae78,c1e6d920,c10850df,c1af9c80,c24b608c,c1af9c80,c17c56c0,c939ae84) at netbsd:cpu_switchto+0x7a
[ 6727.3164359] sleepq_block(0,1,c10850df,c1296770,3,c17c7d40,c1af9c7c,80,c1ccd540,c939aec0) at netbsd:sleepq_block+0x9d
[ 6727.3164359] cv_wait_sig(c1af9c80,c1ccd540,c2368c40,c08fbbc4,c1aeb51c,c1af9ca4,0,c24b61c8,0,c1e5d210) at netbsd:cv_wait_sig+0x100
[ 6727.3164359] pipe_read(c1aeb280,c1aeb280,c939aee4,c17c3a80,1,bfbac0b8,80,c939aedc,1,c1b26004) at netbsd:pipe_read+0x2ab
[ 6727.3164359] dofileread(3,c1aeb280,bfbac0b8,80,c1aeb280,1,c939af60,c24b6020,c1293f5c,c939af9c) at netbsd:dofileread+0x8a
[ 6727.3164359] sys_read(c24b6020,c939af68,c939af60,c1b26004,c9398000,c939af60,c939af68,3,0,0) at netbsd:sys_read+0x60
[ 6727.3164359] syscall() at netbsd:syscall+0x1f7
[ 6727.3164359] --- syscall (number 3) ---
[ 6727.3164359] ae1260d7:
[ 6727.3164359] cpu0: End traceback...

[ 6727.3164359] dumping to dev 0,1 offset 2680
[ 6727.3164359] dump 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 succeeded


[ 6727.3164359] rebooting...

The above was extracted from http://releng.netbsd.org/b5reports/i386/2018/2018.06.17.13.12.25/test.log .
There are more logs at http://releng.netbsd.org/b5reports/i386/commits-2018.06.html#2018.06.17.07.13.02 .
 
>How-To-Repeat:

Inspect the test logs.

>Fix: